1. Field of the Invention
The invention relates to an injector, in particular for fuel injection, with a magnet valve for controlling an injection valve. Such magnet valves are used to control an injection valve of a fuel injection system that has a nozzle needle whose opening and closing position are controllable by the magnet valve, so that injection bores can be opened to inject fuel.
2. Description of the Prior Art
A known magnet valve has a movable armature, which when the magnet assembly of the magnet valve is supplied with electric current lifts from a valve seat in the lower armature chamber. This valve seat is in turn in fluidic communication with the control pressure chamber of the injection valve via one or more (throttle) bores. When the valve seat opens, the pressure in the control pressure chamber of the injection valve drops, and fluid (pressure medium) flows via the bores in the direction of the valve seat and from there into the lower armature chamber.
When the pressure in the control chamber is dropping, the nozzle needle of the injection valve, which is constantly subjected to a high fuel pressure acting in the opening direction, is put into motion, and as a result the injection bores are opened, and the injector can inject fuel.
A common rail injector (CRI) functions in this known mode of operation, and both a main and a preinjection can be achieved with very short injection times. A magnet valve of this kind is known for instance from German Patent Disclosure DE 196 50 865 A1.
Known injectors of the generic type in question also have a return bore, which leads to the lower armature chamber and through which fuel quantities from various portions of the magnet valve and injection valve are returned to the lower armature chamber.
If current is no longer supplied to the magnet valve, then the armature moves downward in response to the restoring force of a restoring spring, and closes the valve seat that leads to the outlet throttle. As a result, the pressure in the control chamber increases again, so that the nozzle needle is moved downward and the injection bores are closed.
When the armature takes a seat on the valve seat, the armature recoils, causing it to open the valve seat again and causing a brief pressure reduction in the control chamber. This delays the closure of the nozzle needle. The armature recoil leads overall to a course of the armature stroke that is approximately equivalent to a damped vibration. This leads to a delayed closure of the nozzle needle, which is disadvantageous particularly if a rapid switching sequence of the magnet valve (preinjections and main injection) is wanted, and which is moreover expressed in a worsening of the emissions and noise values of the engine.
In German Patent Disclosure DE 197 08 104 A1, it is proposed, for reducing armature recoil in a generic magnet valve, to provide a damping device, which cooperates with the movable armature and a stationary part and leads to damping of the after-vibration of the armature. By means of a special embodiment of the armature plate, the armature guide stub, and the sliding part in which the armature bolt extends, various damping devices are achieved in this reference, and interposed adjusting shims can enhance the damping effect. However, especially in one-piece armatures, this principle has proved to be too expensive, and on its own it is not always adequate.